This application relates generally to electro-dynamic swirlers, and especially to combustion devices that comprise electro-dynamic swirlers, and methods for using the same.
Various thrust and power generation apparatuses, e.g., gas turbines, combust a mixture of air and fuel. In gas turbines, fuel-air mixture is continually supplied to a combustor where they are continually burned to produce hot combustion gases. These gases are expanded through one or more turbine stages, creating mechanical power and, in some cases, propulsive thrust. Pulse detonation engines detonate a fuel-air mixture, producing hot combustion gases which have increased temperature and pressure. The hot combustion gases are directed from the engine to produce thrust.
In a pulse detonation engine, as shown in FIGS. 1A-1F, a spark initiates the mixture and starts out as a deflagration which transitions via deflagration to detonation transition (DDT) to a fully developed detonation. The expanding hot combustion products act like a piston, accelerating the flame front. (FIG. 1A) The flame front gets more wrinkled and corrugated (FIG. 1B) and increases flame surface area as it accelerates and transitions to a turbulent flame (FIG. 1C). The increase in flame surface area leads further to an acceleration in propagation velocity and the creation of compression waves (FIG. 1D), which get amplified to shock waves during the acceleration process. If the shock waves are strong enough to increase the gas temperature of the reactant and start interacting within the confinement, a localized explosion takes place (FIG. 1E), which leads to a locally overdriven detonation wave, and a coupling between shock and reaction zone. As soon as this coupling has been established a detonation wave is formed. (FIG. 1F)
Exemplary fuel and air mixtures for pulse detonation engines include gaseous and liquid fuel and air mixtures. One problem with detonations in fuel/air mixtures with low volatility is a long deflagration-to-detonation transition (DDT) length. Attempts have been made to decrease the DDT length by placing obstacles and other turbulence-enhancing geometries inside a detonation chamber. One particular augmentation device is threaded in the interior surface of the inlet end of the detonation chamber with a helical-type thread to provide a ridged surface. Other attempts to decrease the DDT length include using pre-detonators and improving the combination of spark energy and position, detonation chamber geometry, shock focusing, and fuel/air properties. Although some success has been achieved, shorter DDT lengths and time remains a central challenge for low volatility detonation systems, like e.g. liquid fuel systems.
It would therefore be desirable to enhance air-fuel mixing, reduce the DDT length, and/or enhance control over the flame acceleration process and the developing detonation.